Involute (or evolvent) gear drives are known (F. L. Litvin “Teoriya zubchatykh zatsepleniy”, Moscow, Nauka, 1968, 584 pp.), that comply with the basic law of meshing by means of intermating tooth face profiles of paired wheels, with the following overlap ratio (εα) and total overlap ratio (εγ): εα≧1 and εγ≧1. The involute gear drive has some disadvantages, such as low structural flexibility of the tooth face profile (danger of edge engagement phase and presence of pole engagement phase, low degree of tooth contact tightness) and high sensitivity to process and deformation irregularities of the tooth contact along a line of teeth.
Novikov's spatial ‘out-of-pole’ (herein further called ‘extra-pole’) gear drive is known (M. L. Novikov “Zubchatye peredachi s novym zatsepleniem”, published by VVIA im. N. E. Zhukovskogo, 1958, 186 pp.), and satisfies the basic law of meshing by means of axially intermating teeth with addendum mating (εα=0) of their face profiles, convex of radius ρα at a tooth addendum and concave of radius ρf at a tooth dedendum, Δρ=ρf−ρα>0. The Novikov gear drive has disadvantages such as low structural flexibility—lacking a principle ability to design a spur gear and/or narrow-crown drive, necessity to choose the value of Δρ>>0, low degree of tooth contact tightness, and its increased sensitivity to process and deformation irregularities of shape.
Spatial gear drives of mixed engagement are known (G. A. Zhuravlev, Gear Drive, USSR Inventor's Cerificate No. 1185942, IPC F16H1/08, Pri. 20.05.1975, Bulletin No. 15, 2004), with axially intermating teeth, where extra-pole pointwise conjugate sections of the tooth face profiles are circumscribed by concave line of radius ρass at a tooth addendum and convex line of radius ρfss at a tooth dedendum, ρass−ρfss>0, connectable by involute sections with profile angle of base tooth contour α>>αk, with α=α1α and αk<α1α (αk is theoretical pressure angle of extra-pole arc-shaped sections; α1α is profile angle at lower boundary point of main arc-shaped section at a tooth addendum) and increased meshing angle αtw.
Due to employment of two effects: (G. A. Zhuravlev “The Mixed Gearing Engagement Systems. Proceedings of Ninth World Congress on the Theory of Machines and Mechanisms”, Vol. 1, Italy, Milano, 1995, p.p. 433-437), an effect of the super-additive IP kinematical principle (in contrast to the additive one, with simple adding of engagement components when they are combined in the mixed engagement) and an effect of contact curvature (the effect of considerable, exceeding the one that may be described by a solution of the Hertz flat contact problem, influence of the increasing of contact tightness for elastic bodies to lowering the contact stresses and, as a consequence, revelation of a principle ability to improve greatly pole and extra-pole phases of engagement), such drive is free from lost of the tooth contact surface, contact strength of the pitch point is augmented up to the maximum extent, parameters of the contact durability (pole and extra-pole) of the engagement phases are equalized, and particular features of the shape of its tooth face profile ensure increased smoothness of its operation and low bending stresses.
The known gear drive has certain disadvantages such as limited structural flexibility regarding an increase of contact tightness (and employment of the curvature effect) during phases of extra-pole meshing, as well as in selecting parameters of longitudinal (εβ≧1) tooth shape.
Spatial gear drives of mixed engagement are known (G. A. Zhuravlev, Mixed-Engagement Gearing, EUROPEAN PATENT No. 0293473, F16H55/08, 29.07.92 and Russian Federation Patent No. 1075041, IPC F16H55/08, Bulletin No. 7, 1984), based on the kinematical principle of mixed IP.
Tooth face profiles comprise involute sections and main pointwise conjugate arc-shaped sections (convex at a tooth addendum and concave at a tooth dedendum, with parameters depending on the sign and absolute levels of inter-axle distance deviations Δαw>0 and Δαw<0), which are continuously connectable to each other by additional arc-shaped sections (small-sized construction sections, using effect of concentrator curvature, i.e. an influence effect of increasing the geometrical concentrator curvature at certain loading parameters, according to a cross bending pattern, onto the lowering of bending stresses: G. A. Zhuravlev, “The Principle of the Kinematical Independence to the Mixed Toothed Engagements. Proceedings of ISMM '97 International Symposium <<MACHINES and MECHANISMS>>, YUGOSLAVIA, BELGRADE, 1-3.9.1997): concave section of radius ρpa at a tooth addendum and convex section of radius ρpf at a tooth dedendum.
This approach provides for a kinematical independence principle: involute sections have α>>α1α. Due to a greater teeth overlap and lesser drive sensitivity to the inter-axle distance deviations, active width of toothed crown bw may be decreased to bw≈0.7px (where px is an axial pitch), with considerable improvement of the parameters of its bending durability, vibro-acoustics and service life. The disadvantages of this solution are limitations of structural flexibility regarding employment of the curvature effect and increase of contact tightness during all engagement phases.
Gear drives of mixed engagement are known (G. A. Zhuravlev, USSR Patent No. 1839700, IPC 5F16H1/20, 55/08, Pri. 24.09.1986, Bulletin No. 48-47, 1993), formed by multi-flow elements of IP type with shifted engagement phases of tooth face profiles of different pairs of interacting toothed crowns, e.g. composite wheels. In each individual pair of the interacting toothed crowns, involute (at α>>α1α) and pointwise conjugate sections of the tooth face profiles form independent engagement phases with interrupted continuity of their kinematical engagement and discrete existence (only for single points and local portions of the profiles) of the common tangential plane at teeth contact place, ensuring (due to relative offset of the discrete engagement phases) face overlap ratio εα≧1 and intermating of the paired wheels.
The component of pointwise conjugacy of the convexo-concave sections of the tooth profiles is combined with refusal from conditions of axial overlap, forming pitch-line gear contact, increased contact tightness during all engagement phases, lack of axial forces at the engagement. At the same time, the complying with condition εα≧1 imposes limitations on the structural flexibility of the multi-flow IP drive regarding employment of effects of curvature and contact tightness increase.
Gear drives of mixed engagement with face teeth intermating are known (G. A. Zhuravlev, Russian Federation Patent No. 1571330, IPC F16H 55/08, 25.04.1988, Bulletin No. 22, 1990), taken here as prototype (the closest prior art device), based on the mixed IP kinematical principle and the effect of contact curvature.
Tooth face profiles of the IP drive have involute (quasi-involute) sections and extra-pole piecewise conjugate and/or pointwise conjugate (convex at a tooth addendum and concave at a tooth dedendum) sections, mating each other at theoretical points of contact of extra-pole sections (α=αk=α1α), creating inflection at the theoretical point of contact at a tooth dedendum.
The involute sections create independent engagement phase, with a face overlap ratio εα≧1, and have different (by both sides from the inflection) types of contact between tooth profiles at boundary points, from convexo-concave to biconvex. The drive on the whole has contact of pitch-line type without conditions of axial overlap and is characterized by employed curvature effects with increased contact tightness (up to pitch-line contact during extra-pole engagement phases), increased levels of super-additivity of the mixed engagement and structural flexibility of the face and longitudinal tooth shapes. Such parameters like engagement dynamics, combination of running-in ability with wear-resistance, vibro-acoustics, loading capability, and service life of the gear drive are improved.
Limitations of the structural flexibility of the known drive (conditions of face and total teeth overlap εα>1 and εγ>1) restrain the increase of contact tightness (engagement angle αtw and/or height values of the extra-pole pointwise conjugate sections) during various engagement phases and level of super-additivity of the mixed engagement.